Re: [PATCH 0/3] target: Fix queue-full callback error signaling

[Potnuri Bharat Teja <bharat@chelsio.com>]

On Friday, March 03/31/17, 2017 at 10:02:09 +0530, Nicholas A. Bellinger wrote:
Hi Nicholas,
>    Hi Bharat & Co,
> 
>    On Thu, 2017-03-23 at 11:06 +0530, Potnuri Bharat Teja wrote:
>    > On Monday, October 10/31/16, 2016 at 10:55:51 +0530, Nicholas A.
>    Bellinger wrote:
>    > >    From: Nicholas Bellinger <nab@linux-iscsi.org>
>    > Hi Nicholas,
>    > This patch series fixes the post failures due to Send Queue overflow
>    when
>    > tested along with Sagi's "iser-target: avoid posting a recv buffer
>    twice", which
>    > goes on top of these 3 patches.
>    >
>    > Combined patches series(Nicholas's, Sagi's) works fine.
>    > Tested with iWARP iser.
>    >
>    > As these changes are critical for devices with lower sg resources,
>    hoping this
>    > series will be queued for next RC.
>    >
>    > Reviewed-by: Potnuri Bharat Teja <bharat@chelsio.com>
>    > Tested-by: Potnuri Bharat Teja <bharat@chelsio.com>
> 
>    As mentioned, the original three patches along with Sagi's have been
>    applied to target-pending/master.
Thanks a lot!
> 
>    Thank you for your testing and patch review.
> 
>    I'm still considering if they should be CC'ed for stable, considering
>    AFAICT they are pretty much a requirement for iser-target to be stable
>    with iw_cxgb4.  It should be OK to include the series back to v4.1.y
>    stable, but I'm reviewing the target change again just to be sure.
Yes, It would be nice to have them backported to v4.1
> 
>    Also, I've been thinking a bit more about the hung tasks you reported
>    earlier during session reinstatement + repeated queue full preceding
>    Sagi's patch here:
> 
>    [1]http://www.spinics.net/lists/target-devel/msg14868.html
> 
>    and have some clarity as to what was going on..
> 
>    The issue is that queue full handling for TFO->write_pending(),
>    TFO->queue_data_in() and TFO->queue_status failures will retry
>    indefinitely until they successfully complete, and currently do not
>    honor se_cmd quiesce that occurs during normal session reinstatement.
> 
>    Which means that if a fabric driver fails any of these three TFO
>    callbacks forever, the se_cmd descriptor will never be properly quiesced
>    back to fabric driver code, resulting in hung tasks you observed while
>    session shutdown waits for this action to complete.
> 
>    So as-is, this patch series doesn't address this particular scenario but
>    doesn't make it any worse either..  ;)
> 
>    That said, it's fine to merge this series now to allow iser-target +
>    iw_cxgb4 to function, and I'll be looking into addressing the infinite
>    queue_full + session reinstatement scenario for target-core in separate
>    patch series.
Thanks, I shall get back to you with some more debug in the above scenario.
> 
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